Air Emissions Management
Emissions Reporting Methodology
We calculate emissions from a variety of sources in our drilling, completions and production operations. To determine our overall greenhouse gas (GHG) inventory, we inventory a range of emissions sources, including flares, storage tanks, fugitive emissions from equipment leaks, engines, liquids unloading, pneumatic devices and electricity usage.
In this report, we include direct emissions (Scope 1) and indirect emissions (Scope 2) as defined by the IPIECA/API/IOGP Petroleum Industry Guidelines for Reporting Greenhouse Gas Emissions, on an operated basis. Our Scope 1 direct emissions from U.S. facilities are calculated using EPA’s Greenhouse Gas Mandatory Reporting Rule. We calculate our U.K. emissions using the Environmental and Emissions Monitoring System, and in our other international facilities we use the API Compendium of Greenhouse Gas Emissions Methodologies for the Oil and Gas Industry. Our Scope 2 indirect emissions are calculated based on purchased electricity usage using EPA’s eGrid (Emissions & Generation Resource Integrated Database) emission factors.
We calculate three greenhouse gas emissions from our operations: carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). We then express these emissions as a single value, carbon dioxide equivalent (CO2e). This takes into account the impact of each compound in the atmosphere relative to CO2. To get our final CO2e emissions, we multiply our CH4 emissions by 25 and N2O emissions by 298 (the Global Warming Potentials of each gas compared to CO2 over a 100-year timeframe) to put them all in the same context.
In 2018, Marathon Oil participated in Environmental Partnership workshops covering industry best practices and new technologies for preventing, finding and detecting emissions. We are a founding member of this voluntary group of U.S. oil and natural gas companies with a mission to continuously improve the industry’s environmental performance by taking action, building knowledge and fostering collaboration among stakeholders. We participate in the partnership’s environmental performance programs aimed at reducing emissions of methane and volatile organic compounds (VOC), which include:
- Phase-out of high-bleed pneumatic controllers
- Monitoring manual liquids unloading operations to minimize emissions
- Leak detection and repair
In line with our climate-related risk mitigation strategy, Marathon Oil seeks to reduce our operational impacts from greenhouse gas (GHG) emissions. We evaluate our performance using GHG and methane emissions intensity, expressed as carbon dioxide equivalent (CO2e) emissions per barrel equivalent of all hydrocarbon produced. We believe the intensity rate is a more comparable measurement over time because it takes into account our overall activity level, including portfolio changes from acquisitions and dispositions.
In 2018, our global GHG intensity increased 15%, compared to 2017. The increase was primarily due to higher flaring in our North Dakota Bakken asset from ongoing regional gas pipeline capacity constraints. In response to this increase in emissions intensity, Marathon Oil is actively evaluating a number of emission reduction technologies for commercial viability.
We achieved a methane intensity decrease of 19% in 2018. To manage methane emissions intensity, we have eliminated high-bleed pneumatic controllers from our operations, use ultra-high efficiency flares, and reduce flash emissions by installing vapor recovery towers (VRT) and vapor recovery units (VRU) where feasible.
In accordance with our Responsible Operations Management System (ROMS), our emission reduction management strategies are applied at each stage of activity: well planning, facility design and engineering, equipment selection and ongoing maintenance.
Some highlights of our air emission mitigation strategies include:
01. INFRARED CAMERAs for leak detection
In 2018, Marathon Oil recorded a .1% leak rate across the more than 1 million components surveyed at OOOOa facilities.
Gas leaks occur for a variety of reasons, including installation issues, the failure of seals between connections and equipment corrosion.
We repair leaking equipment as soon as practicable. Infrared camera monitoring, along with maintenance and operating practices, helps us minimize air emissions from company facilities. Training for infrared camera operators includes certification on thermal contrast, gas plume motion, camera distance limitations and camera adjustments for varying environmental conditions.
All four U.S. business units use infrared cameras to detect leaks at new facilities. The scope and frequency of our leak detection programs are driven by regulatory requirements and other risks, such as facility size and production throughput.
02. Audio, visual and olfactory (AVO) inspections
AVO inspectors use their senses of hearing, sight and smell to help determine if a facility is operating normally. A trained inspector can detect gas leaks.
To mitigate the risks associated with gas leaks, Marathon Oil utilizes qualified individuals to conduct routine AVO inspections of our production locations. A program to survey, prioritize, address and verify is applied with regulations dictating the frequencies.
Field employees are trained to perform AVO inspections for possible leaks as a part of their overall competency training. New employees must demonstrate competency in safety and operating requirements before conducting field work without the supervision of more experienced employees.
03. Weighted thief hatches with high-performance gaskets
Adequately weighting thief hatches reduces the likelihood that vapors will escape from inside storage tanks. Gasket materials that hold up to the elements also reduce the likelihood of tank emissions.
When designing facilities, Marathon Oil considers thief hatch weight and gasket material and selects products that reduce the likelihood of emissions from thief hatches.
Air Emission Mitigation: Additional Strategies
Pneumatic controllers help control different process variables, such as pressure, temperature or fluid levels in tanks or vessels. We select pneumatic controllers based on site-specific needs. Low-bleed or intermittent-bleed, gas-driven pneumatic controllers emit less gas than high-bleed pneumatic controllers. Mechanical controllers operate with zero emissions.
Marathon Oil has completed our plans to eliminate routine usage of high-bleed pneumatic controllers in our U.S. assets.
For new facilities in Oklahoma, we install emissions-free mechanical controllers where operationally feasible instead of gas-driven pneumatic controllers. We’re also evaluating retrofitting facilities in Oklahoma.
Using air instead of gas-powered pneumatic devices to run pad controllers and pumps reduces GHG emissions.
The use of instrument air has significantly decreased emissions in our Eagle Ford business unit where there is access to electric power lines.
Reduced emissions completions (REC)
This practice captures gas produced during well completions and workovers following hydraulic fracturing. Portable equipment is brought on site to separate the gas from the solids and liquids produced during the high-rate flowback. The gas can then be delivered to the sales pipeline or routed to a control device instead of being vented. RECs help reduce methane, volatile organic compounds (VOC) and hazardous air pollutants (HAP) emissions during well cleanup. Routing gas to a sales line can eliminate or significantly reduce the need for flaring.
Marathon Oil uses 100% reduced emissions completions in our U.S. operations.
Ultra high-efficiency flares
These combust more gas than traditional flares, leading to lower methane, carbon monoxide (CO) and VOC emissions.
In the Bakken, we use ultra-high efficiency flares on all of our new installations. This has resulted in substantially lower VOC and CO emissions.
Natural gas liquids (NGL) removal units
The units reduce volumes of gas flared by condensing NGLs that would otherwise be flared.
We are deploying NGL units to recover a portion of gas in the Bakken.
Vapor recovery units (VRUs) and vapor recovery towers (VRTs)
A VRU recovers vapors in crude oil or condensate tanks. A VRT is a tall pressure vessel installed between the production separators and liquid storage tanks, which captures pressurized gas that would otherwise be sent to the tanks.
VRUs and VRTs are used at many of our new facilities to capture additional natural gas and reduce the likelihood of emissions from tank thief hatches.
Plunger lifts use the reservoir’s natural energy to build up pressure and allow the well to flow, reducing the number of times the well must be vented.
Approximately .07% of our emissions are from liquids unloading. We use several methods to further minimize emissions associated with unloading liquids from the well. In Oklahoma, we have installed six to eight plunger lifts per year over the past five years.
Other methods for liquids unloading include surfactant/foam down the well to reduce the gas velocity needed to overcome liquids in the well, which often helps to reduce the amount of venting.
reduced diesel use
Replacing diesel generators with natural gas-fired generators reduces emissions.
Eagle Ford eliminated the use of non-emergency diesel generators for rod pumps, removing 105 diesel generators from 2014 through 2018. The only diesel generators in the asset are emergency generators at some central facilities.
In the Permian Basin, we removed all diesel-fired generators and replaced them with natural gas-fired units in early 2018. The asset continues to install natural gas-fired units to reduce associated emissions on a per horsepower basis.
Where available, Oklahoma switched from diesel generators used during flowback to natural gas generators in 2018.
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